Considering Argonians can live underwater and their homeland is mostly swamp, I'm reckoning that their armor will be water resistant.
I'm guessing tit will be along the lines of the dreugh armor in Morrowind or crossed with the dark brotherhood armor from Oblivion, seeming that many Argonians are hatched to be assassins. Dreugh was one of the best armors in Morrowind.
http://images.uesp.net//a/a4/MW_Armor_DreughM.jpg
In fact considering that dreugh armor only contained the parts that argonians could wear and considering the lore of argonians into Morrowind I wouldn't be surprised if Dreugh armor was actually an Argonian made armor. Surely if it was a Dunmer armor it would have boots and a full face like all the other Dunmer armors.
I don't see argonians using metal plate armors but rather armor made from animal hides stitched carefully together giving full movement and lightness to swim, creep and jump. Morrowind neighbors Black marsh to the north and looking at some of the creatures in Morrowind such as Dreugh, Guar, Kagouti etc I'm sure that Black marsh will have some similar creatures for the Argonians to be able to construct some good armors like the dreugh armor.
any one else got any thoughts?